Flare stack tip

ABSTRACT

A FLARE STACK TIP HAS AN INLET FOR RECEIVING A DUMP GAS, AN OUTLET FOR EMITTING THE DUMP GAS TO THE ATMOSPHERE FOR SUBSEQUENT COMBUSTION AND MEANS FOR INTRODUCING AMBIENT AIR INTO THE DUMP GAS STREAM PRIOR TO ITS LEAVING SAID OUTLET.

2 Sheets-Sheet 1 f Y i A. E. `moc-rola FLARE STACK TIP Jan. 12, 1971 Filedepy 27, 196e United States Patent O U.S. (11.431-202 9 Claims ABSTRACT OF THE DISCLOSURE A Hare stack tip has an inlet for receiving a dump gas, an outlet for emitting the dump gas to the atmosphere for subsequent combustion and means for introducing ambient air into the dump gas stream prior to its leaving said outlet. f

- The present invention relates to flare stack tip'assemblies. Such assemblies are well known in the petroleum and chemical industries or oil renerie's, vsfhere theirfunction is to burn off Waste gases arising from a particular process. It is desirable that a are stack tip should achieve smokeless, noiseless combustion of the waste gases.

This application is addressed to an improved4v are stack tip which will overcome the disadvantages of the known ilare" stack tips and achieve an improvement in smokeless and noiseless combustion. According to the invention there is provided a flare stack tip including means for introducing ambient air into the .gas stream prior to its leaving the outlet of the stack and combusting. Further, there is provided a method of combustion in a flare stack tip wherein air is introduced into the gas stream prior to its leaving the outlet of the stack and combusting. Further, there is provided a method ofrcombustion in a are stack tip wherein air is introduced into the gas stream prior to its leaving the outlet of thestack and combusting. The means for introducing ambient air into the gas stream can be a series of venturis or preferably one or more air-inducing devices based upon the phenomenon known as the Coanda eiect. There is also provided a (gas stream diverter in the flare stack tip the function of `which is to divert the gas stream radially outwards so as 'to improve the properties of air/ gas cdllision.

A constructional embodiment of the present invention will now be described by way of example only, with reference to the accompanying drawings, wherein:

FIG. l is a side elevation of a are stack tip assembly made in accordance with the invention.

FIG. 2 is a plan view of the assembly of FIG. 1.

FIG. 3 is a part-sectional side elevation of the upper part of the are stack tip; and

FIG. 4 is a sectional side elevation of detail A of FIG. 3 on an enlarged scale.

As shown in FIG. l, a are stack tip `assembly has a tubular member with an upper portion 13 and a lower portion 14. The lower portion 14 is formed with a ange 11 at its lower end for connecting to a fixed stack (not shown). The flare tip proper, designated 30, is connected with the upper portion 13 by any suitable method such as welding and comprises a lower frusto-conical part 1a and an upper tubular part 1. The upper part 1 provides a are nozzle or outlet 50 which is lined with a suitable refr-actoiy material 15. As shown in FIG. 2, three pilot burners 2 of known design are arranged around the outlet 50 of the tip for igniting the emergent gas. Each burner 2 has two pipes 3 and 6 connected with a flame nozzle in known manner and is attached to the -are tip 30 by means of detachable support members 4, 5. The lower end of the frusto-conical part 1a carries a steam manifold 7 which communicates with a steam supply pipe 10 ICC attached to the tubular member by means of bracket 9. The lower part of the steam pipe 10 has a flange 12 for connecting to a main steam supply pipe (not shown).

The construction of the ilare tip 30` is shown in more detail in FIG. 3. VThe are tip 30 has two rings of air inducing devices 40, 41 mounted with their axes extending obliquely relative to the axis of the stack, two of such devices being shown at the right hand `side of the ligure. As shown, the axis of device 40 extends at an angle of about 45 to the axis of the stack and the axis of the device 41 extends at an angle of about 30 thereto. Each air inducing device 40, 41 is an air mover of known design which operates to draw ambient air from outside the stack and drive it into the tip 30 to meet the main gas stream flowing up through the stack. The construction and operation of lthe air-inducing device cc. 40, 41 is based upon the vCoanda effect, and each such device preferably uses steam as an inducing medium, as in this embodiment, although it could use compressed air as an air inducing medium. Steam is fed to each device 40, 41 from the steam manifold 7 via a conduit 42. The tip 30 has two rings of simple locating members 43, 44 which can preferably be pivoted relative thereto. The members 43, 44 are adapted to receive the devices 40, 41 and two such members are shown at the left hand side of the gure.

A gas 'diverter 45 is located within the tip 30 and coaxially thereof. The diverter 45 is carried on support rods 46 extending radially from the walls of the tip 30. The exact construction of the diverter 45 is shown in FIG. 4, where it can be seen that the diverter 45 has two leading walls 46 which form a nose 47 at their juncture. The gas/ air mixture eventually emerges from the outlet 50 whereupon it is ignited by the burners 2.

The operation of the ilare sta-ck tip is as follows:

The gas stream passesl axially up the flare stack in known manner until it meets the nose of the diverter 45 which splits up the gas stream and diverts it towards the walls of the tip. The devices 40, 41 induce and inject ambient air into the gas stream and the particular construction of the diverter 45 and the arrangement of the devices 40, 41 is designed to achieve a gas/air collision Iangle as near t0 90 as possible without causing unnecessary back pressure against gas ow in the stacks. The method of igniting the emergent gas by means of the burners 2 is well known in the art and suffice it to say that the pilot burners of this embodiment can either operate as a natural atmospheric system or as a forced draught system.

The devices 40, 41 may each have working ratio of about 20 lbs. of air induced to l lb. of steam consumed. For complete smokeless combustion, it has been calculated that with the tip of this embodiment of the invention 4 lbs. of air per lb. of flare gas is needed. Thus, a fth of a pound of steam is used for every 1 lb. of ared gas-a considerable improvement over the known methods.

What is claimed is:

1. A flare stack tip having (a) an inlet for receiving a dump gas;

(b) an outlet for emitting said dump gas to the atmosphere for subsequent combustion; and

(c) a plurality of air-inducing devices, the operation of which is in the manner known as the ICoanda effect said devices being arranged in concentric rings with their axes inclined relative to the axis of the tip and being adapted to induce ambient air into said dump gas.

2. A are stack tip having (a) an inlet for receiving a dump gas;

(b) an outlet for emitting said dump gas to the atmosphere for combustion;

(c) a plurality of air inducing devices the operation of which is in the manner known as the Coanda elfect, arranged in two concentric rings around said tip, with the axis of each device being inclined to the axis of the tip; and

(d) means for passing an inducing medium to said devices to cause the latter to inject a mixture of ambient air and inducing medium into said dump gas prior to its emergence from said outlet.

3. A are stack tip having (a) an inlet for receiving a dump gas;

(b) an outlet for emitting said dump gas to the atmosphere for subsequent combustion;

(c) a plurality of air-inducing devices, the operation of which is in the manner known as the Coanda effect said devices being arranged in concentric rings with their axes inclined relative to the axis of the tip and being adapted to induce ambient air into said dump gas; and

(d) means for carrying each air inducing device and permitting said device to pivot in relation to the longitudinal axis of the tip.

4. A are stack tip according to claim 1, wherein each air inducing device is of elongated aerofoil section and uses as an inducing medium uid injected into and transversely to the axis of said device by means of an annulus at the periphery of the inlet of said device.

5. A flare stack tip according to claim 1, wherein the devices are arranged in two concentric rings (a) and (b), each of the devices in ring (a) is arranged `with its axis of air ow extending at an angle of about 45 to the longitudinal axis of the tip, and each of said devices 4 in ring (b) is arranged with its axis of air flow extending at an angle of about 30 to the longitudinal axis of the tip.

6. A flare stack tip according to claim 2, wherein the inducing medium is steam.

7. A are stack tip according to claim 1, wherein each inducing device uses compressed air as an inducing medium and there is further provided means for supplying compressed air to said device.

8. A flare stack tip according to claim 1, wherein the outlet is lined with a refractory material and there is provided pilot burners for igniting the dump gas emitted therefrom.

9. A flare stack tip according to claim 1, wherein therein there is provided a gas stream diverter disposed between the inlet and outlet and arranged to divert the dump gas obliquely-radially outwards relative to the longitudinal axis of the tip.

References Cited UNITED STATES PATENTS 2,052,869 9/1936 Coanda 239-418 2,480,230 8/ 1949 Elster 431--5 2,506,972 5/ 1950 Schellentrager et al. 431-202 2,802,521 8/1957 Campbell et al. 431--202X 3,435,613 4/1969 Eannarino et al. 23--277X EDWARD G. FAVORS, Primary Examiner U.S. C1. XR. 

